Under suitable conditions, microorganisms degrade all natural and many man-made (xenobiotic) organics. Biodegradation and bioconversion of wastes often provide cost effective alternatives to conventional disposal methods. Alternatively, microbial catabolic enzymes provide a tremendously rich source of catalytic activities for beneficial chemical and biochemical transformations. There is a critical need to further understand and harness the biodegradative capabilities of microorganisms to prevent or reduce environmental pollution which can adversely affect human health and well-being. Microbial ring-fission dioxygenases play an essential role in the transformation of resonance- stabilized aromatic compounds to more readily biodegradable aliphatic intermediates. Arthrobacter sp. Strain GFB100 produces 3,4- dihydroxyxanthrone dioxygenase in the catabolism of the three-ring oxygen heterocyclic compound xanthone. Objectives of the proposed research include the purification and characterization of this enzyme. This is necessary for eventually determining the enzyme's fundamental structural features and how it breaks down certain potentially toxic compounds. This information may be useful in designing biological systems for enhance toxic chemical biodegradation. Another objective of the proposed research is to clone and sequence the gene encoding the enzyme and compare its predicted amino acid sequence to similar biodegradation enzymes. This will shed light on the essential features of the enzyme necessary for degradation of potentially toxic multi-ring aromatic chemicals. Students participating in the project will actively participate in scientific research, experimental design, and record keeping. They will also learn methods of protein purification, growth and maintenance of strains, electrophoresis and isoelectric focusing, preparation of antigens, enzyme characterization, gene cloning, and DNA sequence analysis, all useful tools for biomedical research careers at universities, research institutes and in the biomedical industry.